Oblique proximal locking screw in tibial fracture intramedullary nailing: a clinical imaging study of proximity to common peroneal nerve.

Intramedullary nailing (IMN) is the treatment of choice in the surgical management of most tibia shaft fractures. The aim of the study was to evaluate the proximity of the common peroneal nerve (CPN) to the oblique proximal locking screw inserted from the anteromedial to the posterolateral direction. We identified all the patients who underwent the IMN of the tibia between 2008 and 2018. Patients who underwent post-operative computed tomography for any reason were identified. Patients were included if the CPN was visible on the axial slices, the proximal oblique locking screw was used, or the line of the drilling could be reconstructed. Twenty-nine patients met the inclusion criteria. The median length of the intramedullary nail was 345 mm. The median nail diameter was 10 mm. The median number of proximal interlocking screws was 2. All scans were reviewed by the musculoskeletal radiologist for verifying the visibility and marking of the CPN. The mean screw trajectory angle to the CPN was 9° (± 9°). Most of the drilling trajectories passed posterior to the CPN (79%). The depth of the intramedullary nail was on average - 8 mm (± 10 mm). A negative correlation was observed between the depth of the nail and the distance from the CPN (P < 0.001). During the insertion of the oblique proximal locking screw from the anteromedial to the posterolateral direction, the CPN is potentially at risk if the drill is allowed to plunge or an incorrectly long screw is used. Sinking the nail provides a better margin of safety.